Sure the framework is capable of doing all that, you have access to all AppGameKit functions inside your plugin code thats what the wrapper is for.
As for protecting assets, PB has a packer and a cypher lib, you could certainly code a entity encryption system but bear in mind that that protected asset had to be unprotected at some point for agk to load it, you could rip them to memory and encrypt then load in on a memblock, you dont need a plugin for this you can code that in basic look at [href=https://forum.thegamecreators.com/thread/220121]WadPacker
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And the server creating the sprites, sure, just setup a messaging system, the server does not actually call the sprite create function it sends a command to the client to create the sprite.
for a messaging system you want low latency which usually means DONT SEND STRINGS
CONST_CREATE_SPRITE = 100
CONST_IMAGE_A = 101
setup some constants that both the server and client understand CONST_CREATE_SPRITE|CONST_IMAGE_A|100|100|
and send as data, 4 ints travel the net a lot faster than a long ass string, do some bit shifting to make longs you now have 2 longs with HI and LO words.
But, yea, everything you ask is possible with the plugin framework